1. uninstall jinitiator from your computer
2. at your forms builder go to edit -> preferences -> runtime -> press button 'reset to default' and add this to the end of application server url: *?config=jpi*
3. now try running your form with internet explorer 8 (you also may use firefox but should use firefox 3.5 and chrome but chrome is not a browser certified)

I'm assuming you already have installed jdk 1.6 u21+
setting jpi as your config will tell the browser to use java's plugin instead of jinitiator